Evaluation of liquid moisture management properties on hemp woven fabrics treated with liquid ammonia

Abstract

The effects of yarn number and liquid ammonia (L/A) treatment on the liquid moisture management properties (such as wetting time, absorption rate, maximum wetted radius, spreading speed, accumulative one-way transport capability, and overall moisture management capability) of hemp woven fabrics were evaluated by using a moisture management tester on the basis of AATCC test method 195-2011. As a result of the L/A treatment, the crystal structure of hemp fiber was changed from cellulose I into a mixture of cellulose III and cellulose I and its crystallinity was slightly decreased from 66.1% to 57.4%. From scanning electron microscopy analysis, hemp fabric looked swollen and bulked after L/A treatment. The liquid moisture management properties of the L/A-treated hemp woven fabrics showed much better results compared with the untreated ones. Overall moisture management capacity values increased as the yarn number increased and the values of the L/A-treated hemp samples are higher than those of untreated ones. This research could be valuable for the improvement of liquid moisture management properties of hemp woven fabrics.

Keywords

moisture management liquid ammonia hemp overall moisture management capability

The human body is a complex system, which is in equilibrium with its surroundings while performing its vital functions properly. The transport of both moisture vapor and liquid away from the body is called moisture management.¹ Moisture management can be defined as the controlled movement of water vapor and liquid water (perspiration) from the surface of the skin to the atmosphere through fabric.² Moisture management properties of fabrics in clothing are among the most important parameters that determine the wearer’s comfort perceptions, depending on the interaction between the human body and the environment. Based on this, many researchers have examined moisture management properties of fabrics using different test methods and equipment in their studies.^3,4 The moisture management tester (MMT), which was developed by Hu et al.⁵ and has been used frequently in recent years, measures the multi-dimensional transport performance of liquid moisture on the knitted and woven fabrics. Zhou et al.⁶ determined that the overall moisture management capacity of wool/cotton-blended fabrics is better than that for other fabrics types in their study, where they examined the liquid transport properties of pure wool, wool/polyester, and wool/cotton-blended knitted fabrics, which have different weave types. Wang et al.⁷ reported the effect of moisture management on the functional performance of cold protective clothing. Furthermore, various researchers have studied the effects of enzymatic and plasma treatments on the moisture management properties of knitted polyethylene terephthalate (PET) fabrics,⁸ the moisture management properties of wool/polyester and wool/bamboo knitted fabrics for the sportswear base layer,⁹ the evaluation of thermal and moisture management properties on knitted fabrics and comparison with a physiological model in warm conditions,¹⁰ moisture management and absorptivity properties of double-face knitted fabrics,¹¹ moisture management behavior of high-wicking three-dimensional (3D) warp knitted spacer fabrics,¹² moisture management of active sportswear,^13,14 the evaluation of moisture management properties on knitted fabrics made of cotton, viscose, and polyester yarns,¹⁵ the effect of blend proportion on the moisture management characteristics of bamboo/cotton knitted fabrics,¹⁶ and pressure performance and moisture management properties of compression form-fitted athletic wear under different tension ratios and corresponding psychophysical response.¹⁷

On the other hand, since the liquid ammonia (L/A) treatment has been practically done in textile finishing, many researchers have extensively employed the L/A treatment as a pre-treatment for shape stability and for improving the soft hand and physical properties of hemp and other fabrics. In particular, the effect of L/A on the fine structure of linen fabrics,¹⁸ the wear properties of hemp, ramie, and linen fabrics after L/A/crosslinking treatment,¹⁹ and the change of crystal structures of cotton cellulose I and II by L/A²⁰ were investigated. Furthermore, the effect of L/A treatment of silk,²¹ nylon 6,²² and regenerated cellulosic fabrics²³ were studied. From these researches, it is well known that the crystallite form, cellulose I, of native cotton is transformed to cellulose III by NH₃. Ammonia penetrates cellulose relatively easily and reacts with the hydroxyl group after breaking the hydrogen bonds. Therefore, the L/A treatment imparts wrinkle recovery, soft handle, and mechanical properties to cellulose fabrics. Zhang et al.²⁴ reported the effects of L/A treatment on surface characteristics of hemp fiber.

However, there has been little discussion on the moisture management properties of hemp materials by using L/A treatment. Hemp was most likely the first plant cultivated by mankind for its textile use.²⁵ Currently, the interest in hemp is focused on its use as a raw material for the production of environmental friendly clothes.²⁶ For the wearer’s comfort perceptions, perspiration should be transported away from the skin surface, in the form of liquid or vapor, so that the fabric touching the skin feels dry. The present study aims to investigate the effects of L/A treatment on the liquid moisture management properties of 100% hemp woven fabrics prepared with three spun yarns of different yarn number. Their moisture management properties on the basis of the AATCC test method 195-2011²⁷ were evaluated by using the MMT, by which the liquid moisture transport behavior in three dimensions was sensed, measured, and recorded. Changes in the crystalline structure, crystallinity, and morphology after L/A treatment were also investigated.

Materials and methods

Desized and scoured hemp woven fabrics were obtained from Jangnoksoo Hemp Co., Korea. Yarn numbers of the hemp woven fabrics were N_m 24, 48, and 60, with which woven fabrics were prepared. The yarn numbers of warp and weft yarns in the materials are equal. All samples were conditioned at 20 ± 1℃ and 65 ± 2% relative humidity (RH) for 48 h prior to testing according to ASTM D1776. The specifications of the fabric samples are shown in Table 1. Fabric mass per unit area and fabric thickness were measured using ASTM D 3776/D D3776M-09a and ASTM D1777-96, respectively. The cover factor and cloth cover of the hemp fabrics were determined by using the following formula²⁸
$Coverfactor = \frac{n}{\sqrt{N}}$
(1)

$Cloth cover = K_{1} + K_{2} - \frac{K_{1} K_{2}}{28}$
(2)
where n is ends or picks per inch, N is cotton count (N = 0.5906 × N_m), K₁ is the cover factor of the warp direction, and K₂ is the cover factor of the weft direction. The cover factor and cloth cover of the hemp fabrics before and after L/A treatment are shown in Table 2.
Table 1.
Fabric structure, count, weight, thickness, and cloth cover of the fabric samples

Yarn number (N_m) Fabric structure Fabric count
Cloth cover Fabric weight (g/m²) Thickness (mm)

ends/in picks/in

24 Plain 63 52 22.3 200 0.52

48 Plain 85 70 21.6 139 0.43

60 Plain 92 69 20.7 103 0.30

Table 2.
Cover factor and cloth cover of hemp woven fabric samples before and after liquid ammonia (L/A) treatment

Cover factor/cloth cover Yarn number (N_m)

24
48
60

Untreated L/A treated Untreated L/A treated Untreated L/A treated

Warp cover factor 16.7 18.2 15.9 17.7 14.9 17.5

Weft cover factor 13.8 14.9 13.1 14.3 11.1 12.0

Cloth cover 22.3 23.4 21.6 23.0 20.7 22.1

The material samples were treated with 100% L/A (NH₃) for 2 s at −33.4℃ under a tension-free condition using the processing equipment²⁹ shown in Figure 1.
Figure 1.
Processing equipment for liquid ammonia treatment.

X-ray diffraction patterns of the fibers were measured with a Bruker D 8 Discover of GADDS (Germany). The operating conditions were Cu-Kα radiation, voltage 40 kV, current 40 mA, inclinometer revolution speed 3°/min, and scan from 5° to 40° of 2θ. The degree of crystallinity of hemp fiber before and after L/A treatment was calculated by the following equation
$Crystallinity (%) = [I_{c} / (I_{a} + I_{c})] \times 100$
(3)
where I_c is the integrated diffraction intensity of the crystalline region and I_a is the integrated diffraction intensity of the amorphous region based on 2θ = 18°.

The surface and cross-section of hemp fabric sample with N_m 60 spun yarn before and after L/A treatment were observed morphologically by scanning electron microscopy (Jeol, JSM-6700F) at a beam voltage of 20 kV at room temperature. All the specimens were coated with gold using an ion sputter coater (Jeol, JFC-1 100E).

According to AATCC test method 195-2011, wetting time, absorption rate, maximum wetted radius (MWR), spreading speed (SS), accumulative one-way transport capability (OWTC), and overall moisture management capability (OMMC) of hemp woven fabrics were measured by using a MMT (SDL Atlas Co.). A schematic diagram of the MMT apparatus is given in Figure 2.^5,12,14,17 The MMT is designed to sense, measure, and record the liquid moisture transport behaviors in multiple directions. The principle is based on the fact that when there is moisture transport in the fabric, the contact electrical resistance of the fabric will change and the value of the resistance change depends on two factors: the components of the liquid and the water content in the fabric. The liquid components are fixed, so that the electrical resistance measured is related to the water content in the fabric.³⁰ A special solution was prepared according to AATCC test method 195-2011. A total of 9 g of sodium chloride was dissolved in 1 l of distilled water to achieve 16 ± 0.2 mS of solution conductivity and the solution was dropped onto the fabric’s top surface. The test solution will then transfer onto the fabrics in three directions: spreading outward on the top surface (inner) of the fabric; transferring through the fabric from the top surface to the bottom surface (outer); spreading outward on the bottom surface of the fabrics. During the test, the same quantity of solution (0.15 g) was applied onto each specimen’s top surface automatically by the instrument. The test liquid is dispensed through the gland to the top surface of the fabric sample, which is designed as an inner surface that will be in touch with the human skin. The pump time is 20 s and total test time was 120 s. All specimens (8.0 cm × 8.0 cm) were conditioned and tested in standard atmosphere conditions. Based on the signals measured, a set of indices is calculated according to AATCC test method 195-2011; the indices are graded and converted from value to grade based on a five-grade scale (1–5). The five grades of indices represent the following: 1 – poor; 2 – fair; 3 – good; 4 – very good; 5 – excellent. Table 3 shows the range of values converted into grades. An average of five readings was taken for each sample. The obtained results were evaluated by using the SPSS for Windows 19.0 statistical package program. Yarn number and L/A treatment were taken as two parameters, while moisture management properties are taken as dependent. To determine the statistical importance of the variance, analysis of variance (ANOVA) tests were applied.^7,11,15 During the ANOVA procedure, we set two parameters (yarn number and L/A treatment), three levels (N_m 24, 48, and 60), and five replications. In order to deduce whether the parameters were significant or not, p-values were examined. As is known, if the p-value of a parameter is greater than 0.01 (p > 0.01), the parameter will not be significant and should be ignored.
Figure 2.
Schematic diagram of moisture management tester apparatus: (a) sweat gland; (b) top sensor; (c) fabric inner (next to skin) side; (d) fabric outer side; (e) bottom sensor; (f) copper ring.

Table 3.
Grading table of all indices on moisture management properties.²⁷

Index Grade

1 2 3 4 5

Wetting time (s)

Top ≥120 20–119 5–19 3–5 <3

Bottom ≥120 20–119 5–19 3–5 <3

Absorption rate (%/s)

Top 0–9 10–29 30–49 50–100 >100

Bottom 0–9 10–29 30–49 50–100 >100

Max wetted radius (mm)

Top 0–7 8–12 13–17 18–22 >22

Bottom 0–7 8–12 13–17 18–22 >22

Spreading speed (mm/s)

Top 0.0–0.9 1.0–1.9 2.0–2.9 3.0–4.0 >4.0

Bottom 0.0–0.9 1.0–1.9 2.0–2.9 3.0–4.0 >4.0

One-way transport capability (%) <–50 –50–99 100–199 200–400 >400

Overall moisture management capability (OMMC) 0.00–0.19 0.20–0.39 0.40–0.59 0.60–0.80 >0.80

Results and discussion

X-ray diffraction and scanning electron microscopy analyses

The X-ray diffraction patterns of hemp fibers before and after L/A treatment are demonstrated in Figure 3. The major diffraction peaks of (002), (101), and (10 $\bar{1}$ ) planes at 2θ = 22.6°, 14.6°, and 16.7°, respectively, of the untreated hemp showed the crystalline forms of cellulose I. The peak at 2θ = 20.7° by (002)/(10 $\bar{1}$ ) planes in the patterns of the treated hemp is a characteristic for cellulose III and the peak at 2θ = 11.7° by (101) planes is a characteristic for cellulose I. It is generally well known that the cellulose I crystalline form of native cotton is transformed to cellulose III by L/A treatment.³¹ However, in the present study, it was shown that the crystal structure of hemp treated with L/A treatment transforms from cellulose I to a mixture of cellulose III and I. This result is also similar to that of ramie treated with L/A treatment.³² The degree of crystallinity of hemp fiber before and after L/A treatment was determined by equation (3). The degree of crystallinity of hemp fiber treated with L/A was 57.4%, and that of the untreated one was 66.1%. Accordingly, the degree of crystallinity of hemp fiber after L/A treatment was decreased by about 13.2%. This is because the orientation of the cellulose molecular chain in the crystalline region was disordered due to the influences of good penetration and intra-crystalline swelling of hemp cellulose by L/A treatment and, as a result, the amorphous region in the cellulose molecular chain of the treated hemp fiber was relatively increased.
Figure 3.
X-ray diffraction patterns of hemp fibers before and after liquid ammonia treatment.

Figures 4(a) and (b) show the surface morphology of untreated and L/A-treated hemp fabrics prepared with N_m 60 yarn, respectively. The yarn space of hemp fabric was significantly compacted due to the swelling and separation of individual fibers by the L/A treatment. Cross-sectional images of untreated (Figure 4(c)) and L/A-treated hemp fabrics (Figure 4(d)) also showed that the fibers became more separated and consequently more bulked after L/A treatment. In addition, these results may be due to the changes of swelling and internal structure in the crystalline and amorphous regions of fibers in the fabric and the yarn space of fabric being compacted from the gap between two yarns after L/A treatment.
Figure 4.
Scanning electron microscopy images of the surface morphology ((a) untreated; (b) treated) and cross-sectional morphology ((c) untreated; (d) treated) of hemp woven fabrics prepared with N_m 60 yarn after liquid ammonia treatment.

Moisture management properties

The results of the moisture management properties and variance analysis of our samples are summarized in Tables 4 and 5, respectively. In order to determine whether two parameters according to the yarn number and L/A treatment were significant or not, p-values were examined. As the p-values in Table 5 were much less than 0.01, the results of the moisture management properties, such as wetting time, absorption rate, MWR, SS, OWTC, and OMMC, according to the two parameters of yarn number and L/A treatment were found to be statistically significant.
Table 4.
The results of moisture management properties of hemp woven fabrics untreated and treated with liquid ammonia (L/A)

Index Yarn number (N_m)

24
48
60

Untreated L/A treated Untreated L/A treated Untreated L/A treated

Wetting time (s)

Top 1.94 ± 0.21 (5) 1.87 ± 0.24 (5) 3.84 ± 0.11 (4) 2.43 ± 0.12 (5) 3.37 ± 0.21 (4) 2.43 ± 0.15 (5)

Bottom 2.04 ± 0.25 (5) 1.97 ± 0.26 (5) 4.31 ± 0.17 (4) 2.71 ± 0.15 (5) 3.46 ± 0.15 (4) 2.23 ± 0.22 (5)

Absorption rate (%/s)

Top 22.06 ± 1.23 (2) 60.00 ± 1.30 (4) 16.65 ± 1.54 (2) 51.53 ± 1.09 (4) 19.35 ± 1.01 (2) 27.21 ± 1.24 (2)

Bottom 21.62 ± 1.26 (2) 49.91 ± 0.94 (3) 25.91 ± 0.98 (2) 63.31 ± 1.03 (4) 49.54 ± 1.01 (3) 62.08 ± 1.13 (4)

Max wetted radius (mm)

Top 20.00 ± 1.58 (4) 30.00 ± 0.71 (5) 20.00 ± 1.00 (4) 25.00 ± 1.58 (5) 20.00 ± 0.71 (4) 30.00 ± 1.41 (5)

Bottom 20.00 ± 1.41 (4) 30.00 ± 1.00 (5) 25.00 ± 1.41 (5) 25.00 ± 1.00 (5) 20.00 ± 1.00 (4) 30.00 ± 0.71 (5)

Spreading speed (%/s)

Top 1.86 ± 0.11 (5) 7.65 ± 0.42 (5) 2.17 ± 0.12 (3) 4.08 ± 0.22 (5) 2.24 ± 0.17 (3) 4.22 ± 0.22 (5)

Bottom 1.93 ± 0.15 (5) 7.48 ± 0.41 (5) 2.14 ± 0.11 (3) 3.96 ± 0.21 (4) 2.17 ± 0.13 (3) 4.12 ± 0.20 (5)

One-way transport capability (%)^a –73.68 ± 2.23 (1) –62.72 ± 2.73 (1) 342.59 ± 4.16 (3) 129.12 ± 4.19 (3) 335.82 ± 3.91 (4) 211.16 ± 3.56 (4)

OMMC 0.28 ± 0.03 (2) 0.36 ± 0.02 (2) 0.56 ± 0.02 (3) 0.59 ± 0.01 (3) 0.64 ± 0.01 (4) 0.68 ± 0.01 (4)

( ) Grade for each sample.

a
Negative one-way transport capability indicates that water content on the top surface is higher than at the bottom surface.

OMMC: overall moisture management capacity.

Table 5.
Analysis of variance tables of the results of moisture management properties according to two parameters: (a) yarn number; (b) liquid ammonia treatment

Source Sum of square Mean of square F-value p-value

(a)

Wetting time

Top 10.0352 5.0176 1194.67 0.000

Bottom 10.7424 5.3712 1810.52 0.000

Absorption rate

Top 1822.9074 911.4537 1380.85 0.000

Bottom 348.3774 174.1887 171.89 0.000

Max wetted radius

Top 50 25.0000 25.00 0.000

Bottom 50 25.0000 25.00 0.001

Spreading speed

Top 410.7272 205.3636 583.09 0.000

Bottom 417.6434 208.8217 608.75 0.000

One-way transport capability (%) 128992.2272 64496.1136 96,152.83 0.000

OMMC 0.2642 0.1321 1317.00 0.000

(b)

Wetting time

Top 6.3518 3.1759 639.44 0.000

Bottom 8.4182 4.2091 1418.80 0.000

Absorption rate

Top 43.9022 21.9511 64.54 0.000

Bottom 1356.3074 678.1537 1017.08 0.000

Max wetted radius

Top 58.4000 29.2000 37.12 0.000

Bottom 50.0000 25.0000 25.00 0.001

Spreading speed

Top 59.3034 29.6517 3306.88 0.000

Bottom 56.7126 28.3563 10,374.26 0.000

One-way transport capability (%) 323,152.8640 161,576.4320 489,476.73 0.000

OMMC 0.1248 0.0624 110.12 0.000

p-value for 99% significance ≤0.01, df is 2, and error is 6 for all variables.

OMMC: overall moisture management capacity.

Wetting time

Wetting time denotes the time period in seconds when the top and bottom surfaces of the fabrics begin to be wetted after the test is started. The wetting time of hemp woven fabrics treated with L/A is given in Figure 5. As is clear from the Figure 5, all fabric samples in the inner and outer sides showed fast grades. Moreover, the fabric samples treated with L/A treatment in the inner and outer sides showed very fast grades of wetting time. Thus, the wetting time of the L/A-treated samples was faster than that of the untreated ones. This may be explained by the increase of closeness of the yarn space in the fabric because the cloth cover of each fabric sample increased by about 4.9–6.5% after L/A treatment, as shown in Table 2. The wetting time of the top surface for all fabric samples is generally faster than that of the bottom surface. This result may be based on water resistance and water absorption characteristics of the fabric structure, including the fabric’s geometric and internal structure and the wicking characteristics of its fibers and yarns.
Figure 5.
Wetting time values of hemp woven fabrics before and after liquid ammonia treatment: (a) top surface (inner); (b) bottom surface (outer).

Water content versus time

The typical MMT relative water content versus time (0–120 s) graphs of the top and bottom surfaces of the untreated samples are given in Figures 6(a)–(c), and those of the L/A-treated samples are given in Figures 6(a′)–(c′), respectively. In the Figure 6, the green line (UT) indicates the inner parts (top surface) that would be in contact with body skin during perspiration, while the blue line (UB) indicates the outer parts (bottom surface) of the fabrics. The difference between absorbing capacities and the transmission of sweat and also evaporation performances can be explained by these graphs. For the first 20 s, the machine dispensed liquid solution onto the top of the fabric. The closeness of the blue line through the green line within 20 s determines the transmission performance. The blue line comes over the green line if the water transmission from the inner part to the outer part increases. Moreover, the slope of the lines after 20 s indicated higher evaporation performance. The water contents of the top and bottom surfaces suddenly increased for all samples. This is due to the hydrophilic characteristics of hemp, which quickly absorbs the water molecules and transfers water quickly. For the untreated samples of Figures 6(a)–(c), the water content dramatically increased during the dispensing time at around 6 s, while the starting time of increase for L/A-treated samples, Figures 6(a)’–(c)’ was around 3 s. This is due to the reduction of the quantity of water remaining in the fibers and the better capillary effect for the liquid moisture transport by L/A treatment. When the peak values are compared, it is clear that the L/A treatment had significant effects on water content and absorption rates. The peak values also demonstrated the absorption rate values in Table 4. The water content of both the top (inner) and the bottom (outer) part at 20 s for the L/A-treated samples was higher when compared to that for the untreated samples, suggesting that the L/A-treated fabric samples should have better absorbing capacity and L/A treatment has an important advantage, namely quick drying performance, due to the better transmission of sweat between the top and bottom surfaces.
Figure 6.
Water content versus time graphs of the top and bottom surfaces of hemp woven fabrics before and after liquid ammonia treatment. Untreated: (a) N_m 24; (b) N_m 48; (c) N_m 60. Treated: (a′) N_m 24; (b′) N_m 48; (c′) N_m 60. (Color online only.)

Water location versus time and absorption rate

MWR values are also defined in Figure 7 as water location versus time images by the MMT to clarify the amount of synthetic sweat in spreading areas for the top and bottom surfaces. The black color represents dry parts and the blue color represents wetted parts, while the lighter blue color means there are more wetted parts. The top and bottom surfaces of the untreated fabric samples in Figures 7(a)–(c) were almost wetted at the upper 20 cm radius. Moreover, the top and bottom surfaces of the L/A-treated fabric samples in Figures 7(a′) and (c′) were completely wetted up to the MWR values, which was not the case for the N_m 48 sample (Figure 7(b′)). It is obvious that the black colored area in the untreated images has turned into a blue color by L/A treatment. In addition, it is evident that a noticeable improvement in wetting time and SS performances in Table 4 were observed by L/A treatment. On the other hand, the absorption rate defines the liquid moisture absorption ability for the top and bottom surfaces of the fabric samples during the initial change of water content.
Figure 7.
Water location versus time images of hemp woven fabrics before and after liquid ammonia treatment. Untreated: (a) N_m 24; (b) N_m 48; (c) N_m 60. Treated: (a′) N_m 24; (b′) N_m 48; (c′) N_m 60. (Color online only.)

The absorption rate of the top and bottom surfaces of the hemp woven fabrics treated with L/A are given in Figure 8. As can be seen, the top absorption rate is slowest whereas the bottom absorption is highest for all fabric samples except the N_m 24 sample. The absorption rate of the fabric samples treated with L/A treatment in the inner and outer sides showed very fast grades of absorption rate compared to the untreated fabric sample. This indicates that the L/A treatment has an effect on the absorption rate of the hemp woven fabrics, while the effect of yarn number was negligible.
Figure 8.
Absorption rate of hemp woven fabrics before and after liquid ammonia treatment: (a) top surface (inner); (b) bottom surface (outer).

Max wetted radius and spreading speed

MWR top and MWR bottom (mm) are defined as the MWR at the top and bottom surfaces, respectively, where the slopes of total water content (U top or U bottom) become greater than Tan (15°) for the top and bottom surfaces, respectively. MWR (mm) values of hemp woven fabrics treated with L/A are given in Figure 9. As can be seen from Figure 9, MWR top and MWR bottom values of the hemp woven fabrics treated with L/A are large or very large at 20–30 mm (the limited maximum radius of the test apparatus is 30 mm). In addition, the MWR of the L/A-treated samples was higher than that of the untreated samples. This may be again explained by the increase of closeness of the yarn space in the fabric after L/A treatment, which might facilitate the capillary condensation of moisture. In addition, L/A treatment reduces the quantity of water remaining in the fibers and it also increases the moisture quick-drying ability. However, there was no effect of yarn number on the MWR. On the other hand, SS is defined as the accumulative SS from the center to the MWR. As can be seen from Figure 10, SS values of the L/A-treated samples are higher than those of the untreated samples. SS values of the top and bottom surfaces are similar. Although the effect of yarn number is not significant, the SS becomes faster after L/A treatment.
Figure 9.
Maximum wetted radius of hemp woven fabrics before and after liquid ammonia treatment: (a) top surface (inner); (b) bottom surface (outer).

Figure 10.
Spreading speed of hemp woven fabrics before and after liquid ammonia treatment: (a) top surface (inner); (b) bottom surface (outer).

One-way transport capability

Accumulative OWTC is the difference of the accumulative moisture content between the two surfaces of the sample, which indicates the liquid transfer through the fabric from the upper surface to the lower surface. OWTC values of hemp woven fabrics treated with L/A are given in Figure 9 and the values are compared with the grading scale in Table 3 (<–50: poor; –50–99: fair; 100–199: good; 200–400: very good; >400: excellent). The fabric samples prepared with N_m 48 and 60 were found to have a higher than good OWTC with three grades. However, the fabric sample of N_m 24 has a negative OWTC, indicating that water content on the top surface is higher than at the bottom surface. This is assumed because the values of thickness and cloth cover of hemp woven fabrics prepared with N_m 24 were higher than those of N_m 48 and 60 from the structural and physical properties given in Table 1. The OWTC values of the fabric samples treated with L/A were increased as the yarn number increased, whereas the OWTC values of the untreated fabric samples were not affected by yarn number. As shown in Figure 11, this result may be because the OWTC values of the fabric samples prepared with N_m 48 and 60 have a shorter wetting time for the top surface than for the bottom surface due to the modification of the internal structure in the crystalline and amorphous region by the L/A treatment.
Figure 11.
One-way transport capability of hemp woven fabrics treated with liquid ammonia.

Overall moisture management capability

OMMC is defined as an index to indicate the overall capability of the fabric sample to manage the transport of liquid moisture, which includes three aspects of performance: moisture absorption rate of the bottom side; one-way liquid transport capability; and the spreading drying rate of the bottom side. OMMC values of hemp woven fabrics treated with L/A are given in Figure 12. The L/A-treated and untreated fabric samples prepared with coarse yarn of N_m 24 showed fair OMMC with grade 2. The L/A-treated and untreated samples prepared with medium yarn of N_m 48 showed good OMMC with grade 3. Moreover, the L/A-treated and untreated samples prepared with fine yarn of N_m 60 showed very good OMMC with grade 4. That is to say, the OMMC values of the L/A-treated and untreated hemp woven fabrics increased as the yarn number increased. As is shown from the figure, the OMMC values of the L/A-treated hemp woven fabrics are higher than that of untreated ones. OMMC values increased as the yarn number increased. As shown in Table 4, it can be concluded that the samples of N_m 24, 48, and 60 are fair, good, and very good for moisture management fabrics, respectively.
Figure 12.
Overall moisture management capacity (OMMC) of hemp woven fabrics treated with liquid ammonia.

Conclusion

The effect of L/A treatment on the liquid moisture management properties of 100% hemp woven fabrics prepared with three spun yarns of different yarn number in order to improve the comfort perceptions in clothing was investigated by using the MMT. From the X-ray diffraction data, the crystal structure of hemp fiber was changed from cellulose I into a mixture of cellulose III and cellulose I and its crystallinity was slightly decreased from 66.1% to 57.4% after L/A treatment. Scanning electron microscopy analysis showed that L/A treatment made the hemp fabrics swollen and bulked. We could measure dynamic liquid transfer in a fabric in three directions in one step. All the liquid moisture management indices, such as wetting time, absorption rate, MWR, SS, and accumulative OWTC of the L/A-treated hemp woven fabrics showed much better results compared with the untreated ones. OMMC values increased as the yarn number increased and the values of the L/A-treated hemp samples are higher than those of the untreated ones. This result suggested that L/A treatment improved the liquid moisture management properties of hemp woven fabrics significantly.

Yarn number (N_m)	Fabric structure	Fabric count	Cloth cover	Fabric weight (g/m²)	Thickness (mm)
24	Plain	63	52	22.3	200	0.52
48	Plain	85	70	21.6	139	0.43
60	Plain	92	69	20.7	103	0.30

Cover factor/cloth cover	Yarn number (N_m)
Warp cover factor	16.7	18.2	15.9	17.7	14.9	17.5
Weft cover factor	13.8	14.9	13.1	14.3	11.1	12.0
Cloth cover	22.3	23.4	21.6	23.0	20.7	22.1

Index	Grade
Wetting time (s)
Top	≥120	20–119	5–19	3–5	<3
Bottom	≥120	20–119	5–19	3–5	<3
Absorption rate (%/s)
Top	0–9	10–29	30–49	50–100	>100
Bottom	0–9	10–29	30–49	50–100	>100
Max wetted radius (mm)
Top	0–7	8–12	13–17	18–22	>22
Bottom	0–7	8–12	13–17	18–22	>22
Spreading speed (mm/s)
Top	0.0–0.9	1.0–1.9	2.0–2.9	3.0–4.0	>4.0
Bottom	0.0–0.9	1.0–1.9	2.0–2.9	3.0–4.0	>4.0
One-way transport capability (%)	<–50	–50–99	100–199	200–400	>400
Overall moisture management capability (OMMC)	0.00–0.19	0.20–0.39	0.40–0.59	0.60–0.80	>0.80

Index	Yarn number (N_m)
Wetting time (s)
Top	1.94 ± 0.21 (5)	1.87 ± 0.24 (5)	3.84 ± 0.11 (4)	2.43 ± 0.12 (5)	3.37 ± 0.21 (4)	2.43 ± 0.15 (5)
Bottom	2.04 ± 0.25 (5)	1.97 ± 0.26 (5)	4.31 ± 0.17 (4)	2.71 ± 0.15 (5)	3.46 ± 0.15 (4)	2.23 ± 0.22 (5)
Absorption rate (%/s)
Top	22.06 ± 1.23 (2)	60.00 ± 1.30 (4)	16.65 ± 1.54 (2)	51.53 ± 1.09 (4)	19.35 ± 1.01 (2)	27.21 ± 1.24 (2)
Bottom	21.62 ± 1.26 (2)	49.91 ± 0.94 (3)	25.91 ± 0.98 (2)	63.31 ± 1.03 (4)	49.54 ± 1.01 (3)	62.08 ± 1.13 (4)
Max wetted radius (mm)
Top	20.00 ± 1.58 (4)	30.00 ± 0.71 (5)	20.00 ± 1.00 (4)	25.00 ± 1.58 (5)	20.00 ± 0.71 (4)	30.00 ± 1.41 (5)
Bottom	20.00 ± 1.41 (4)	30.00 ± 1.00 (5)	25.00 ± 1.41 (5)	25.00 ± 1.00 (5)	20.00 ± 1.00 (4)	30.00 ± 0.71 (5)
Spreading speed (%/s)
Top	1.86 ± 0.11 (5)	7.65 ± 0.42 (5)	2.17 ± 0.12 (3)	4.08 ± 0.22 (5)	2.24 ± 0.17 (3)	4.22 ± 0.22 (5)
Bottom	1.93 ± 0.15 (5)	7.48 ± 0.41 (5)	2.14 ± 0.11 (3)	3.96 ± 0.21 (4)	2.17 ± 0.13 (3)	4.12 ± 0.20 (5)
One-way transport capability (%)^a	–73.68 ± 2.23 (1)	–62.72 ± 2.73 (1)	342.59 ± 4.16 (3)	129.12 ± 4.19 (3)	335.82 ± 3.91 (4)	211.16 ± 3.56 (4)
OMMC	0.28 ± 0.03 (2)	0.36 ± 0.02 (2)	0.56 ± 0.02 (3)	0.59 ± 0.01 (3)	0.64 ± 0.01 (4)	0.68 ± 0.01 (4)

Source	Sum of square	Mean of square	F-value	p-value
(a)
Wetting time
Top	10.0352	5.0176	1194.67	0.000
Bottom	10.7424	5.3712	1810.52	0.000
Absorption rate
Top	1822.9074	911.4537	1380.85	0.000
Bottom	348.3774	174.1887	171.89	0.000
Max wetted radius
Top	50	25.0000	25.00	0.000
Bottom	50	25.0000	25.00	0.001
Spreading speed
Top	410.7272	205.3636	583.09	0.000
Bottom	417.6434	208.8217	608.75	0.000
One-way transport capability (%)	128992.2272	64496.1136	96,152.83	0.000
OMMC	0.2642	0.1321	1317.00	0.000
(b)
Wetting time
Top	6.3518	3.1759	639.44	0.000
Bottom	8.4182	4.2091	1418.80	0.000
Absorption rate
Top	43.9022	21.9511	64.54	0.000
Bottom	1356.3074	678.1537	1017.08	0.000
Max wetted radius
Top	58.4000	29.2000	37.12	0.000
Bottom	50.0000	25.0000	25.00	0.001
Spreading speed
Top	59.3034	29.6517	3306.88	0.000
Bottom	56.7126	28.3563	10,374.26	0.000
One-way transport capability (%)	323,152.8640	161,576.4320	489,476.73	0.000
OMMC	0.1248	0.0624	110.12	0.000

Footnotes

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the research fund of Dankook University in 2014.

References

Haghi

. Moisture permeation of clothing, a factor governing thermal equilibrium and comport. J Therm Anal Calorim 2004; 76: 1035–1055.

Yoo

Barker

. Moisture management properties of heat-resistant workwear fabrics effect of hydrophilic finishes and hygroscopic fiber blends. Text Res J 2004; 74: 995–1000.

Onofrei

Rocha

Catarino

. The influence of knitted fabrics’ structure on the thermal and moisture management properties. J Eng Fiber Fabr 2011; 6: 10–22.

Sakar

Fan

Qian

. Transplanar water transport tester for fabrics. Measurement Sci Technol 2007; 18: 146–1471.

Yeung

. Moisture management tester: a method to characterize fabric liquid moisture management properties. Text Res J 2005; 75: 57–62.

Zhou

Feng

. Characterization of liquid moisture transport performance of wool knitted fabrics. Text Res J 2007; 77: 951–956.

Wang

Tokura

. Effect of moisture management on functional performance of old protective clothing. Text Res J 2077; 77: 968–980.

Karaca

Demir

Oezdogan

. Environmentally benign alternatives: plasma and enzymes to improve moisture management properties of knitted PET fabrics. Fiber Polym 2010; 11: 1003–1009.

Troynikov

Wardiningsih

. Moisture management properties of wool/polyester and wool/bamboo knitted fabrics for the sportwear base layer. Text Res J 2011; 81: 621–631.

10.

Bedek

Salauen

Martinkovska

. Evaluation of thermal and moisture management properties on knitted fabrics and comparison with a physiological model in warm conditions. Appl Ergon 2011; 42: 792–800.

11.

Supuren

Oglakcioglu

Ozdil

. Moisture management and thermal absorptivity properties of double –face knitted fabrics. Text Res J 2011; 81: 1–11.

12.

Bagherzadeh

Gorji

Latifi

. Evolution of moisture behavior of high-wicking 3D warp knitted spacer fabrics. Fiber Polym 2012; 13: 529–534.

13.

Senthilkumar

Sampath

Ramachandran

. Moisture management in an active sportwear: techniques and evaluation. J Inst Eng India Ser 2013; 93: 61–68.

14.

Manshahia

Das

. Moisture management of high active sportwear. Fiber Polym 2014; 15: 1221–1229.

15.

Oener

Atasagun

Okur

. Evaluation of moisture management properties on knitted fabrics. J Text Inst 2013; 104: 699–707.

16.

Prakash

Ramakrishnan

Koushik

. Effect of blend proportion on moisture management characteristics of bamboo/cotton knitted fabrics. J Text Inst 2013; 104: 1320–1326.

17.

Liu

Little

Williams

. Compression form-fitted athletic wear: pressor performance, moisture management properties under different tension ratios, and compressing psychophysical responses. Fiber Polym 2014; 15: 632–644.

18.

Dornyi

Csiszar

Somlai

. Effect of liquid ammonia on the fine structure of linen fabrics. Text Res J 2006; 76: 629–635.

19.

Feng

Zhang

. Wear properties of hemp, ramie and linen fabrics after liquid ammonia/crosslinking treatment. Fibers Text East Eur 2010; 18: 81–85.

20.

Kim

Bae

Lee

. The change of crystal structures of cotton cellulose I and II by liquid ammonia. J Korean Fiber Soc 1995; 32: 150–157.

21.

Lee

Tokuyama

. Ammonia - gas and liquid ammonia treatments of silk fabric. J Appl Polym Sci 2006; 101: 3487–3492.

22.

Lee

Wakida

. Liquid ammonia treatment of nylon 6 fabric. Text Res J 2002; 72: 539–544.

23.

Lee

Wakida

Tokuyama

. Liquid ammonia treatment of regenerated cellulosic fabrics. Text Res J 2005; 75: 13–18.

24.

Zhang

. Evaluation of liquid ammonia treatment on surface characteristics of hemp fiber. Cellulose 2014; 21: 569–579.

25.

Clarke

. The cultivation and use of hemp (Cannabis sativa L.) in ancient China. J Int Hemp Assoc 1995; 2: 26–32.

26.

Kostic

Pejic

Skundric

. Quality of chemically modified hemp fibers. Bioresource Technol 2008; 99: 94–99.

27.

AATCC Test Method 195-2011:2011. Liquid moisture management properties of textile fabrics.

28.

Booth

. Principles of textile testing, London: Butterworths, 1983.

29.

Lee

. Mechanical properties and hand evaluation of hemp woven fabrics treated with liquid ammonia. Fiber Polym 2016; 17: 143–150.

30.

Li Y, Xu W and Yeung KW. Moisture management of textiles. Patent 6,499, p.338 B2, USA, 2000.

31.

Kim

Bae

Lee

. The change of crystal structures of cotton cellulose I and II by liquid ammonia. J Korean Fiber Soc 1995; 32: 150–157.

32.

Lee

Bae

Lee

. Dyeing and mechanical properties of ramie fabrics treated with liquid ammonia, cellulase, and hot water. J Korean Fiber Soc 2001; 38: 250–257.

Yarn number (N_m)	Fabric structure	Fabric count		Cloth cover	Fabric weight (g/m²)	Thickness (mm)
Yarn number (N_m)	Fabric structure	ends/in	picks/in	Cloth cover	Fabric weight (g/m²)	Thickness (mm)
24	Plain	63	52	22.3	200	0.52
48	Plain	85	70	21.6	139	0.43
60	Plain	92	69	20.7	103	0.30

Cover factor/cloth cover	Yarn number (N_m)
	24		48		60
	Untreated	L/A treated	Untreated	L/A treated	Untreated	L/A treated
Warp cover factor	16.7	18.2	15.9	17.7	14.9	17.5
Weft cover factor	13.8	14.9	13.1	14.3	11.1	12.0
Cloth cover	22.3	23.4	21.6	23.0	20.7	22.1